Illumination consumes 15% to 25% of the total power in advanced countries. For the requirements of reduced energy consumption, light weight and thin shape, organic light emitting diode (OLED) is considered as a novel illumination source for the next generation. Conventional OLED device is a stack layered structure constructed by a cathode layer, organic material layers, a transparent electrode layer, and a substrate. Because refractive index mismatches between the interferences of the layered structure and the waveguide effect, a light produced by the organic layers will be reflected back to the substrate, the transparent electrode layer, or the organic layers and/or emits out of the substrate after several reflections with a decayed intensity or even to disappear. Accordingly, a novel method to improve light extraction efficiency of the OLED is called for.